Apart from you're choosing a message greater than the modulus, another thing that might be confusing you is that, in this case, $C \equiv P \bmod N$.

That is, you take your message, 65, which is equivalent to 10 modulo 55, and encrypt it, and the result is 10, because $10^{13} \bmod 55 = 10$, So, when you decrypt it, you take the ciphertext 10, and naturally get the plaintext back as 10, as $10^{37} \bmod 55 = 10$.

This "ciphertext is the same as the plaintext" is an artifact of using a tiny $N$; it does happen on real size RSA modulii, but with extremely low probability if the plaintext was chosen randomly.